This invention relates to a luminescent display panel, namely, a fluorescent or phosphorescent display panel, which comprises a substantially planar anode assembly, a glass cover having integral peripheral flange portions hermetically sealed to the anode assembly, and a plurality of lead-out conductors hermetically sealed between the assembly and the glass cover along at least one of the flange portions. This invention relates also to a method of manufacturing a luminescent display panel of the type described.
A recent luminescent display panel is usually for a plurality of displays or digits. Each digit, as called herein, may be a numeral, a letter, a symbol, or the like. The display panel comprises a substantially planar anode assembly and a glass cover having integral peripheral flange portions hermetically sealed to the assembly by an interposed layer of fused frit glass. Within a vacuum space enclosed by the hermetically sealed anode assembly and glass cover, the display panel comprises a plurality of luminescent anode segments comprised by the assembly for the respective digits, at least one hot cathode over the anode segments, and a grid between the cathode and the anode segments for each digit. The display panel further comprises lead-out conductors for electrically leading the anode segments, cathode, and grids outwardly of the vacuum space. As will later be described, the lead-out conductors are arranged along at least one of the flange portions and hermetically sealed in that portion of the frit glass layer which is interposed between the assembly and the last-mentioned flange portion.
A luminescent display panel of the type described further comprises a transparent and electroconductive film on that surface of the glass cover which faces the anode assembly and is herein called an inside surface for brevity. It may be mentioned here that the display panel is put into operation by making the cathode emit thermal electrons and by selectively supplying electric voltages to the anode segments and the grids by an external or peripheral electric circuit so as to make the electrons bombard the selected anode segments and that the display panel is usually placed together with the peripheral circuit in a casing having a transparent window plate for allowing the displays to be viewed therethrough. The film serves as means for preventing accumulation of stray electrons and other charges on the inside surface with one end of each cathode brought into electric contact therewith through a support therefor and also as an electrostatic shield for shielding the display panel from electric charges which inevitably accumulate on the casing window plate. The film is therefore more effective when the resistivity thereof is rendered lower. Attempts have therefore been directed to reduction of the film resistivity. On the other hand, it has been usual on sealing the glass cover to the anode assembly to press them together so as to avoid formation of pin holes through the frit glass layer along the lead-out conductor portions sealed in the frit glass layer. Some or all of the lead-out conductors are therefore liable to come into substantial electric contact at least partially with the film portion formed on the flange inside surface to be undesiredly shorted by the film portion and to thereby adversely affect the yield of the luminescent display panels.